Centre Garry Ringrose could be in contention to face Wales in the Six Nations after replacing the injured Robbie Henshaw in Ireland's squad.
Ringrose has been battling ankle trouble since January but was drafted into Ireland's ranks on Monday, with Henshaw sidelined for three to four months with shoulder trouble.
Ireland will be forced to rearrange their midfield in the absence of British and Irish Lion Henshaw, with Chris Farrell and now Ringrose among those in the frame to wear the No.13 shirt.
Henshaw suffered a suspected dislocated shoulder in the act of scoring his second try in Ireland's 56-19 win over Italy on February 10.
"Garry Ringrose comes in to train with the squad following the injury to Robbie Henshaw," the Irish Rugby Football Union (IRFU) confirmed in a statement.
Ringrose has won 11 caps since his 2016 debut, with the 23-year-old growing into a pivotal performer for head coach Joe Schmidt.
Ireland remain hopeful that tighthead prop Tadhg Furlong and locks Iain Henderson and James Ryan will be fit in time for Saturday's Aviva Stadium encounter.
Hooker Rob Herring and halfback Luke McGrath have both picked up injuries and should miss the Wales clash, as Ireland bid to extend their 100 per cent record in this year's Six Nations.
"Tadhg Furlong, Iain Henderson and James Ryan are progressing well through their respective rehab programmes," read the IRFU statement.
"Niall Scannell will again train with the squad following an elbow injury to Rob Herring in Ulster's game against Edinburgh.
"John Cooney will also train with Ireland this week following the knee injury sustained by Luke McGrath in Leinster's game against Scarlets."
England have been given a clean bill of health for their Six Nations clash against Scotland with Nathan Hughes on course to start at No.8.
Any lingering doubt over Owen Farrell and Joe Launchbury has lifted, the former overcoming an unspecified lower leg injury and the latter available after missing last Friday's open training session at Twickenham for load management reasons.
Hughes has been proving his fitness during gruelling sessions at England's training base after recovering from the knee ligament damaged sustained on Wasps duty in mid-December.
The No.8 has made one club appearance since returning several weeks ahead of schedule but starts at Murrayfield after Sam Simmonds was ruled out by a shoulder problem.
"Everyone's fully fit for selection this weekend," forwards coach Steve Borthwick said.
"Nathan's worked really hard, really diligently and he looks in really good shape. He's healed very fast which is great.
"While our strength and conditioning and medical team have worked incredibly hard, the credit has to go to Nathan for the work he's done while he's been injured.
"We want to make sure all of our players are ready for Test matches, that's why we train at the intensity level we train at.
"Nathan gives us different strengths to Sam. He's an outstanding ball carrier. His effect on the group has grown.
"He's excellent with younger players, helping them mentally. He's grown as a player in terms of the influence he has throughout as a leader as well."
Wales have been handed a major boost ahead of Saturday's Six Nations clash in Ireland with Dan Biggar, Taulupe Faletau, Leigh Halfpenny and Liam Williams all declared fit to play.
Flyhalf Biggar missed their first two games - a win over Scotland and loss to England - with a shoulder problem, while a knee injury has sidelined No.8 Faletau since December.
Back Williams had been laid low by a groin injury but proved his fitness as he scored for Saracens in a 13-3 win at Sale Sharks in the English Premiership on Friday.
Fullback Halfpenny pulled out of Wales' last game, which they lost 12-6 to England at Twickenham, with a foot infection.
Together with winger George North, who missed the win over Scotland with a knee injury but came off the bench against England, it means Wales now have five of their British & Irish Lions available for a must-win game in Dublin after starting their Six Nations campaign with a major injury crisis.
Loose forward Ross Moriarty, who did not play for his club Gloucester at the weekend after hurting his shoulder against England, has also been passed fit, Wales assistant coach Robin McBryde told Wales Rugby Union TV.
"It's nice to have headaches in a few positions. It's always good to have plenty to choose from and there's a competitive edge to the squad. It will be a tough call on a few individuals but we're looking forward to having those discussions later," he said.
Coach Warren Gatland will name his team for the Ireland clash on Tuesday.
